Metallic tubes are commonly used to carry fluid in the form of gas or liquid throughout various fluid circuits in many industries. This is especially true in the aerospace industry, due to the lightweight and strong mechanical features of the metallic tubes. For example, thin-walled aluminum and stainless steel tubing is often utilized within an aircraft to carry oxygen and hydraulic fluid for various applications, such as to breathing apparatuses and to and from vehicle brakes.
The fluid circuits typically contain a vast number of interlock joints, which reside between the tubing and the end fittings, such as ferrules. The current technique used to join the different sized tubes and ferrules, is referred to as a roller swaging process. During this process, a tube is inserted into a ferrule while the ferrule is constrained using a clamp. The tube is then expanded into the ferrule using a roller. The inner walls of the ferrule typically contain grooves within which the tube is expanded. An interlock is created between the tube and the ferrule due to the expansion and deformation of the tube against the inner walls and into the grooves of the ferrule.
Another technique that is commonly used to join metallic tubes to end fittings is referred to as Gas Tungsten Arc Welding (GTAW), which is a fusion welding process. The formed joints produced from fusion welding are often rejected by penetrant inspection, pressure testing, or by radiographic inspection and must be weld repaired. A weld formed joint may need to be repaired as many as three times, at significant costs.
A desire exists to increase the operating lifetime of a mechanical or fluid tight joint. Thus, there exists a need for an improved leak tight joint between a tube and a ferrule and a technique for forming the leak tight joint that may be applied to various fluid circuit applications. It is desirable that the improved technique be economical, have an associated quick production set-up time, and account for different sized tube and ferrule combinations.